L9965P datasheet(21/104 Pages) STMICROELECTRONICS

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3.4.3

Wake-up via peripheral SPI

The IC can be woken up by any valid SPI frame. A wake-up condition is acknowledged when the following pattern

is received:

1. A NCS high to low transition

2. 24 SCK pulses

3. A NCS low to high transition

To prevent the logic being stuck in the wake-up detection state upon incomplete patterns, the

tSPI_WAKEUP_TIMEOUT is started upon every NCS assertion, and the wake-up pattern shall end before timeout

expiration, otherwise it is discarded.

Wake-up frames are not decoded, so their content may be arbitrary.

Note:

It is strongly recommended to send READ commands to avoid inadvertent write operations in case the device is

already awake.

When a correct wake-up sequence is acknowledged, the event is latched in the SPI_WAKEUP bit located in the

INTERNAL_STATUS register. The latch-set pulse also triggers the start of the tSPI_COMM_TIMEOUT communication

timeout. Such a timer is intended to avoid the IC being left unintendedly in a high consumption power state in

case the controller is unresponsive:

•

The tSPI_COMM_TIMEOUT is reset and restarted in case a valid frame is received (no CRC error and correct

number of SCK pulses).

•

The tSPI_COMM_TIMEOUT is reset and stopped in case a high level is detected on CWUP. From that moment

on, moving the device to a low power state requires setting CWUP low.

Figure 5. Wake-up condition by peripheral SPI

VALID

NCS

DISCARDED

tSPI_WAKEUP_TIMEOUT

t=0

SCLK

3.4.3.1

SPI wake-up electrical parameters

All parameters are tested and guaranteed in the following conditions, unless otherwise noted: all supplies

according to the Table 3; TJ according to the Table 2.

Table 16. SPI electrical parameters

Symbol

Parameter

Test condition

Min Typ Max Unit

tSPI_WAKEUP_TIMEOUT

Timeout for receive of wake-up

frame

Guaranteed by SCAN

0.4

NCS, SDI,

SDO, SCLK

tSPI_COMM_TIMEOUT

Communication timeout started

in case of wake-up via

peripheral SPI

Guaranteed by SCAN

NCS, SDI,

SDO, SCLK

tSPI_WAKEUP_TIME

IC wake-up latency

From the NCS low to high

transition to the IC in

NORMAL (full NVM

download)

NCS, SDI,

SDO, SCLK

L9965P

Functional description

DS14702 - Rev 4

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